1. Field of the Invention
The invention relates to an assembly comprising a high-voltage generator and X-ray device for use in the general field of radiology.
2. Description of the Prior Art
In order to produce x-radiation, certain installations comprise a so-called X-ray unit. This term is usually understood to mean a device comprising, within a single enclosure referred-to as a shield housing, an X-ray tube for producing x-radiation and means for generating on the one hand the high-voltage supply which is applied to the anode and to the cathode of said X-ray tube and on the other hand the voltages for heating the filament or filaments with which the cathode is equipped. The high voltage is obtained from an alternating-current low voltage which is conveyed to the interior of the shield housing via low-voltage leads and applied to a high-voltage transformer. The alternating-current high voltage developed by said transformer is applied to the anode and to the cathode either directly or via a rectifying device, depending on the type of operation which is contemplated. The voltage used for heating the cathode filament is obtained from one or two low-voltage transformers which are in turn supplied, for example, by means of leads which carry the alternating-current low voltage.
An arrangement of this type usually applies to relatively low values of power consumed by the X-ray tube (values substantially equal to or lower than 50 KW). In the case of higher-power assemblies, the general arrangement is usually different and consists in separating the high-voltage generator from the X-ray tube or in other words placing the high-voltage generator outside the housing. In this design, the high-voltage generator is connected to the X-ray tube by means of wires constituting a pair of high-voltage cables. At least one of these high-voltage cables is of the type which provides high electrical insulation resistance by reason of the fact that the high voltage applied between the cathode and the anode of the X-ray tube may have a high value (of the order of 80 to 150 KV).
One of the advantages offered by an X-ray unit with respect to the system constituted by a high-voltage generator located outside the shield housing lies in the fact that it does not entail any need to provide electric cables having high insulation resistance. Thus only a few low-voltage insulated leads are necessary for the purpose of supplying power to a unit of this type. It is indeed a fact that, in an X-ray installation, the housing which contains the X-ray tube is a particularly mobile element and the cable such as a high-insulation-resistance cable which is attached to the housing constitutes a considerable bulk by reason of the relatively rigid structure made necessary by its electrical insulation properties. Furthermore, although cables having high insulation resistance (dielectric strength) are commonly employed in the X-ray equipment industry, they are in fact very costly. The capital outlay involved is increased even further by the special connecting means required by a cable of this type at the point of penetration into the housing.
The X-ray unit is nevertheless subject to disadvantages since the weight and bulk of this unit are greater than those of the assembly consisting of the housing which contains the X-ray tube alone. This gives rise in particular to mechanical problems in the design of X-ray examination tables or other systems which are to be equipped with said unit.